Transparent polarized light-emitting device

ABSTRACT

A polarized light-emitting device is fabricated by a method that includes forming a radiation-emitting layer. The radiation-emitting layer includes a radiation-emitting material that emits radiation having a wavelength included in an emission wavelength band. The radiation-emitting material is disposed between a transparent anode and a transparent cathode. An optically active reflective layer is disposed on the polarized light-emitting device. The optically active reflective layer is configured to reflect radiation having a wavelength included in a reflection wavelength band of the optically active reflective layer. The reflection wavelength band of the optically active reflective layer is adjusted to at least partially encompass the emission wavelength band of the radiation-emitting layer.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part and claims priority to U.S.application Ser. No. 12/580,931, filed Oct. 16, 2009, now U.S. Pat. No.8,253,153, which is a non-provisional application that claims thebenefit of U.S. Provisional Application No. 61/136,965, filed Oct. 17,2008 and titled TRANSPARENT POLARIZED LIGHT-EMITTING DEVICE, both ofwhich are expressly incorporated herein by reference in their entirety.

TECHNICAL FIELD

This disclosure relates to a transparent polarized light-emittingdevice.

BACKGROUND

Organic light-emitting diodes (OLEDs) are optoelectronic devices made byplacing a layer of organic material between two electrodes. When avoltage potential is applied to the electrodes and current is injectedthrough the organic material, visible light is emitted. Due to the highpower efficiency, low cost of manufacture, and durability of OLEDs, andthe fact that they are lightweight, OLEDs are often used to createvisual displays for portable electronic devices.

SUMMARY

In one general aspect, a transparent directional polarizedlight-emitting device includes a transparent anode and a transparentcathode, a radiation-emitting layer between the anode and the cathode,an optically active reflective layer with a reflection band that matchesa chirality and at least partially encompasses a wavelength band ofradiation emitted from the radiation-emitting layer, the opticallyactive light blocking layer located on a side of the radiation-emittinglayer, and a transparent substrate adjacent to the optically activereflective layer.

Implementations may include one or more of the following features. Theradiation-emitting layer may include an organic light-emitting layer.The radiation-emitting layer may include an inorganic light-emittinglayer. The inorganic light-emitting layer may include a quantum dotemitter. The device may include a hole transport layer located betweenthe anode and the radiation-emitting layer. The device may include anelectron transport layer located between the radiation-emitting layerand the cathode. The device may include an electron tunneling barrierlayer located between the cathode and the electron transport layer. Thedevice may include an electron tunneling barrier adjacent to theradiation-emitting layer. The organic light-emitting layer may include anon-racemic compound of chiral organic light emitting molecules. Theorganic light-emitting layer may include glass-forming chiral nematicliquid crystals (GLCs) that are embedded with organic light-emittingdopants, and the organic light emitting layer may emits chiral light.

The transparent cathode may be a spin polarized electrode. Thetransparent cathode may be one of a ferromagnetic electrode and ahalf-metallic electrode. The transparent anode may be a spin polarizedelectrode. The optically active reflective layer may includemorphologically stable glass-forming chiral nematic liquid crystals(GLCs). The optically active reflective layer may include a cholestericliquid crystal.

The device may include a second optically active reflective layeradjacent to the optically active reflective layer, and a reflection bandof the second optically active reflective layer may have an oppositechirality to that of the optically active reflective layer and may atleast partially encompasses a wavelength band of radiation emitted fromthe radiation-emitting layer. The second optically active reflectivelayer may include morphologically stable glass-forming chiral nematicliquid crystals (GLCs). The transparent anode and the transparentcathode transmit may visible light. The optically active reflectivelayer may include a sculptured thin film. The light-emitting layer mayinclude a chiral material.

In another general aspect, a polarized light-emitting device isfabricated by a method that includes forming a radiation-emitting layer.The radiation-emitting layer includes a radiation-emitting material thatemits radiation having a wavelength included in an emission wavelengthband. The radiation-emitting material is disposed between a transparentanode and a transparent cathode. An optically active reflective layer isdisposed adjacent to the radiation-emitting layer. The optically activereflective layer includes glass-forming chiral nematic liquid crystals(GLC), and the optically active reflective layer is configured toreflect radiation having a wavelength included in a reflectionwavelength band of the optically active reflective layer. The reflectionwavelength band of the optically active reflective layer is adjusted toat least partially encompass the emission wavelength band of theradiation-emitting layer.

In another similar general aspect, a polarized light-emitting device isfabricated by a method that includes forming a radiation-emitting layer.The radiation-emitting layer includes a radiation-emitting material thatemits radiation having a wavelength included in an emission wavelengthband. The radiation-emitting material is disposed between a transparentanode and a transparent cathode. An optically active reflective layer isdisposed on the polarized light-emitting device. The optically activereflective layer is configured to reflect radiation having a wavelengthincluded in a reflection wavelength band of the optically activereflective layer. The reflection wavelength band of the optically activereflective layer is adjusted to at least partially encompass theemission wavelength band of the radiation-emitting layer.

Implementations may include one or more of the following features. Theradiation-emitting material may include an organic light-emitting layer.Adjusting the reflection wavelength band of the optically activereflective layer may include heating the glass-forming chiral nematicliquid crystals above a glass transition temperature (Tg) and near acritical point (Tc) of the glass-forming chiral nematic liquid crystals.The optically active reflective layer may be irradiated withelectromagnetic radiation for a time duration sufficient to alter thereflection wavelength band of the optically active reflective layer toat least partially encompass an emission wavelength band of thelight-emitting layer. The optically active reflective layer may cooledto a temperature below (Tg). Irradiating the optically active reflectivelayer may include irradiating the optically active reflective layer withultraviolet (UV) radiation.

Adjusting the reflection wavelength band of the optically activereflective layer may include adjusting a molecular composition of theglass-forming chiral nematic liquid crystals. Adjusting the reflectionwavelength band of the optically active reflective layer may result inchanging a width of the reflection wavelength band. Theradiation-emitting material may include an inorganic light-emittinglayer. The optically active reflective layer may include a first GLCfilm made of a right-handed glassy cholesteric material, and a secondGLC film made of a left-handed glassy cholesteric material, the secondGLC film being adjacent to the first GLC film. Adjusting the reflectionwavelength band of the optically active reflective layer may includeadjusting a molecular ratio of the right-handed glassy cholestericmaterial to the left-handed glassy cholesteric material. The molecularcomposition of both the first GLC film and the second GLC film may beadjusted to adjust the reflection band of the optically activereflective layer.

In some implementations, a second optically active reflective layer maybe deposited on the optically active reflective layer. The secondoptically active reflective layer and the optically active reflectivelayer have opposite chirality. The reflection wavelength band of thesecond optically active reflective layer may be adjusted to at leastpartially encompass the emission wavelength band of the light-emittinglayer. The optically active reflective layers may be depositedconsecutively, the reflection wavelength band of the second opticallyactive reflective layer may be adjusted on a separate substrate, and theoptically active reflective layer may be bonded to one side of thetransparent polarized light emitting device after the reflectionwavelength band of the second optically active reflective layer isadjusted.

In some implementations, the optically active layer is deposited on atransparent substrate. The transparent substrate may be located betweenthe optically active reflective layer and the light-emitting layer.

In some implementations, the optically active reflective layer mayinclude a holographic optical recording material layer. Adjusting thereflection wavelength band of the optically active reflective layer mayinclude irradiating a holographic optical recording material layer withtwo or more collimated object beams that successively interfere with acommon collimated reference beam to generate several multiplexedreflection holograms on the holographic optical recording materiallayer. The object beams may be circularly polarized, may have the samechirality, may have a specified wavelength to at least partiallyencompass the emission wavelength band of the radiation-emitting layer,and may be incident to the holographic optical recording material layerat a series of angles chosen to maximize the reflection efficiency overa desired field of view at the specified wavelength.

In some implementations, adjusting the reflection wavelength band of theoptically active reflective layer may result in changing the incidentangles at which the reflection wavelength band is achieved.

In some implementations, the optically active reflective layer may havea chirality, such that the optically active reflective layer isconfigured to reflect radiation having a chirality matching thechirality of the optically active reflective layer. The fabricationmethod may further include adhering a pre-fabricated broad-band circularpolarization filter between the light-emitting layer and the opticallyactive reflective layer. The circular polarization filter may have achirality that is opposite the chirality of the optically activereflective filter.

In some implementations, the fabrication method may include adhering aprefabricated radiation-collimating layer between the radiation-emittinglayer and the optically active reflective layer. Theradiation-collimating layer may have an optical property of limiting thedirection of radiation that is emitted by the radiation-emitting layerto an angle less than 40 degrees from normal relative to a surface ofthe polarized light emitting device.

In some implementations, the prefabricated light-collimating layer maybe a photonic crystal composite film or a micro-louver film.

Implementations of the described techniques may include hardware, amethod or process, a device, an apparatus, or a system. The details ofone or more implementations are set forth in the accompanying drawingsand the description below. Other features will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 show examples of a directionally biased light-emittingdevice.

FIG. 3A shows an example of a directionally biased light-emitting devicethat includes two optically active reflective layers.

FIG. 3B shows an example of a directionally biased light-emitting devicethat includes a light-collimating layer.

FIGS. 4A and 4B show examples of a directionally biased light-emittingdevice that includes one optically active reflective layer.

FIGS. 5A and 5B show examples of directionally biased light-emittingdevices that include an organic light-emitting diode (OLED) stack.

FIG. 6A shows an example of a directionally biased light-emitting devicethat includes an organic light-emitting diode (OLED) stack.

FIG. 6B shows an illustration of emission characteristics from thedevice shown in FIG. 6A.

FIG. 7 shows an example process for fabricating a directionally biasedlight emitting device.

FIGS. 8A-8C illustrate an example process of pixilating a phototunableliquid crystal.

FIGS. 9A-11A each show a perspective view of an example directionallybiased light emitting device.

FIGS. 9B-11B respectively show a cross-sectional view of thedirectionally biased light emitting devices shown in FIGS. 9A-11A.

FIG. 12 shows a stacked transparent light-emitting device.

FIG. 13 shows another stacked transparent light-emitting device.

DETAILED DESCRIPTION

A transparent device that emits radiation from one side, or primarilyfrom one side, is described. In particular, an optically activereflective material is placed on a transparent electroluminescencedevice such that radiation emitted from a light-emitting layer in thedevice emanates only from one side of the device, or primarily from oneside of the device, while ambient light is transmitted by both sides ofthe device. The device emits chiral radiation having a range ofwavelengths, and a reflection band of the optically active reflectivematerial is tuned to match both the helicity and the wavelength of theradiation emitted from the device such that the optically activereflective material reflects the emitted radiation. In this manner, thetransparent electroluminescence device may be directionally biased suchthat emitted radiation emanates from only one side of the device, orprimarily from one side of the device, rather than from both sides ofthe device.

The disclosed techniques relate to a particular application of organiclight-emitting diode (OLED) technology. In particular, the disclosedtechniques relate to transparent OLEDs (TOLEDs) that exploit thespin-polarization and the wavelength of emitted light to achieveunidirectional emission. The devices are transparent in that the devicesare made from one or more materials that are at least partiallytransmissive to radiation incident upon the materials. Such TOLEDs maybe referred to as transparent organic unidirectional polarizedlight-emitting diodes (TOUPLEDs). TOUPLEDs may be incorporated into orcoated on to windshields to, for example, allow a driver to seeinformation displayed on the windshield without the information beingvisible from the other side of the windshield. Because the TOUPLED istransparent to ambient light, ambient light passes through thewindshield. Similarly, TOUPLED technology may be utilized on helmets,specifically, military combat helmets or other visualization instrumentsthat include a visor or eyepiece. With such an arrangement, the user ofthe helmet may view information displayed on one side of the visor whilealso being able to see through the visor because ambient light entersthe visor. For example, the TOUPLED may be mounted on a visor of amilitary helmet such that a solider using the helmet may view tacticalinformation displayed on the inside part of a helmet visor while thedisplayed tactical information would not be viewable from the side ofthe visor facing the environment (which is the side on which theoptically active reflective layer is mounted). However, because theTOUPLED is made from materials that are at least partially transparentto ambient light, ambient light continues to pass through the visor.

Referring to FIG. 1, an example of a directionally biased transparentlight-emitting device 100 is shown. The light-emitting device 100includes a light-emitting layer 1, an optically active reflective layer2, and a transparent substrate 4. The light-emitting layer 1 is disposedbetween a first electrode 5 and a second electrode 6. The firstelectrode 5 may be a transparent anode, and the second electrode 6 maybe a transparent cathode. The first electrode 5 and the second electrode6 are transparent to the wavelengths of the radiation emitted from thelight-emitting layer 1 to allow emission of radiation from the device100. Additionally, the first electrode 5 and the second electrode 6 maybe transparent to ambient light such that ambient light may pass throughthe device 100. Although in the example shown in FIG. 1, the firstelectrode 5 is located at a top 7 of the light-emitting layer 1, and thesecond electrode 6 is located at a bottom 8 of the light-emitting layer1, in other examples, the first electrode 5 and the second electrode 6may be arranged in the opposite configuration.

When a positive bias is applied across the first electrode 5 and thesecond electrode 6, the anode injects holes (positive charge carriers)into the light-emitting layer 1, and the cathode injects electrons(negative charge carriers) into the light-emitting layer 1. The holesand electrons recombine in the light-emitting layer 1 and generateexcitons that lead to luminescence. In this manner, the light-emittinglayer 1 emits radiation, preferably in the form of visible light. Asdiscussed in more detail below, the radiation emitted from thelight-emitting layer 1 has a wavelength and a chirality (e.g., theradiation is circularly polarized and has a left-handed or aright-handed orientation or the radiation is elliptically polarized andhas a left-handed or a right-handed orientation).

As discussed in more detail below, the optically active reflective layer2 blocks the radiation emitted from the light-emitting layer 1 byreflecting the emitted radiation back towards the top 7 of thelight-emitting layer 1 and into a light-emission envelope 9 that is onone side of the device 100. In particular, the optically activereflective layer 2 has a reflective band that encompasses, at leastpartially, the wavelengths of the radiation emitted from thelight-emitting layer 1. The reflective band of the optically activereflective layer 2 is the band of wavelengths that are not transmittedby the optically active reflective layer 2. Additionally, the opticallyactive reflective layer 2 has a chirality that matches the chirality ofthe radiation emitted from the light-emitting layer 1.

The optically active reflective layer 2 may be considered to match thechirality and the wavelength of the radiation emitted from thelight-emitting layer 1. By matching the chirality and the wavelength,the index of refraction of the optically active reflective layer 2 maybe tuned, or otherwise modified, such that the wavelength of theradiation emitted from the light-emitting layer 1 is centered on thereflection band of the of the optically active reflective layer 2 andthat the optically active reflective layer 2 reflects radiation having ahelical polarization. Radiation having a helical polarization isradiation that is either elliptically polarized or circularly polarizedand has either a right-handed or left-handed helicity, or chirality. Anelliptically or circularly polarized electromagnetic wave in which theelectric field vector, observed in a fixed plane normal to the directionof propagation while looking in the direction of propagation, rotates ina left-handed direction, i.e., in a counterclockwise direction, and thedirection of propagation is the same as the forward direction of aleft-handed screw when being screwed into a fixed nut.

In some implementations, matching the chirality and the wavelength mayinclude tuning the index of refraction of the optically activereflective layer 2 such that the optically active reflective layer 2 hasa spectral reflection band that includes at least a portion of thewavelengths of the radiation emitted from the light-emitting layer 1. Inthese implementations, the optically active reflective layer 2 may havea reflection band that is centered on the emission band of the emittedradiation, but that is not necessarily the case.

The optically active reflective layer 2 also may be referred to as anoptically active blocking layer or an optically active filter layer. Inthe example shown in FIG. 1, radiation emitted from the light-emittinglayer 1 exits the directionally biased transparent light-emitting device100 through the top 7 rather than through the bottom 8 of thelight-emitting layer 1. However, in other examples, the optically activereflective layer 2 may be located on the side of the top 7 of thelight-emitting layer 1 such that radiation emitted from thelight-emitting layer 1 exits the device 100 through the substrate 4.Thus, the device 100 may be a top-emitting transparent device or abottom-emitting transparent device.

In one implementation, the transparent light-emitting device 100 is atransparent organic unidirectional polarized light-emitting device(TOUPLED). In this implementation, the first electrode 5 is atransparent anode, and the light-emitting layer 1 is a chiral organicmolecule based light emitting layer (which may be referred to as achiral organic light emitting layer). As discussed below with respect toFIGS. 5A and 5B, the TOUPLED also may include an electron tunnelingbarrier layer, a spin polarized cathode (which may be referred to as aspin-cathode), the transparent substrate 4 and, an optically activelight filter layer (which may be referred to as an optically activereflective layer) tuned to the wavelength and chirality of the emittedlight. In one example, the chiralty of the optically active reflectivelayer may be right handed such that right-handed circularly polarizedlight emitted from the light emitting device is reflected by theoptically active reflective layer 2. In other implementations, thelight-emitting layer may be made from, or may include, anylight-emitting material that emits radiation having chiral components(e.g., light that is not linearly polarized).

In another implementation, the light-emitting layer 1 may be an achiralluminophore. An achiral luminophore is a light emitter that does notnecessarily emit chiral radiation but may be configured, structured, orarranged to emit chiral radiation. For example, in this implementation,the light-emitting layer 1 may be an inorganic quantum dot emitter, andthe quantum dot emitter may be arranged in a chiral matrix that produceschiral radiation. In these implementations, the quantum dot emitters aredeposited as a single monolayer. Depositing the quantum dot emitters asa single monolayer may help localize and, thus, control the formationand relaxation of excitons.

In other implementations, any transparent OLED layer that is transparentand does not interfere with the chirality of the emitted and blockedradiation may be used. A material that is not optically active, or isweakly optically active, does not impart a polarization on radiationpassing through the material. Thus, such a material may be used as thetransparent OLED layer. Materials that may be used as a transparent OLEDlayer include glass and ITO. In implementations that use spin-injectors,any transparent OLED layer that minimizes interference with thecharge-spin life time or the chirality of the emitted and blockedradiation may be used.

Referring to FIG. 2, an example of a directionally biased transparentlight-emitting device 200 is shown. The device 200 includes alight-emitting layer 201, an optically active reflective layer 202, atransparent substrate 204, a first electrode 205, and a second electrode206. The device 200 may be similar to the device 100 discussed abovewith respect to FIG. 1, except the transparent substrate 204 is disposedbetween the optically active reflective layer 202 and the light-emittinglayer 201. Similar to the device 100, the device 200 emits polarizedradiation into an emission envelope 209 on one side of the device 200.

Referring to FIG. 3A, an example of a directionally biasedlight-emitting device 300 that includes two light-blocking layers, aright-handed optically active layer 310 and a left-handed opticallyactive layer 320, is shown. The device 300 also includes alight-emitting layer 330, a transparent substrate 340, a first electrode350, and a second electrode 365. As discussed in more detail below withrespect to FIGS. 5A and 5B, radiation emitted from the light-emittinglayer 330 may be chiral radiation (e.g., circularly or ellipticallypolarized light). Depending on the configuration of the light-emittingdevice 300, the chiral radiation may include approximately equal amountsof chiral light with right-handed helicity and chiral light withleft-handed helicity, or the emitted chiral radiation may includeprimarily chiral light with right-handed helicity or primarily chirallight with left-handed helicity.

In the example shown in FIG. 3A, the light-emitting layer 330 emitsradiation that includes chiral light with left-handed helicity andchiral light with right-handed helicity. Chiral light 355 withright-handed helicity is reflected from the optically active reflectivelayer 310, and the chiral light 360 with left-handed helicity isreflected from the optically active reflective layer 320. Thus, theradiation emitted from the bottom 370 of the light-emitting layer 330 isreflected through the top 380 of the device 300 rather than exitingdevice through both the bottom 390 and the top 380. Because thechirality of helically polarized light conserves orientation uponreflection off of an optically active material, but reverses orientationupon reflection off of a non-optically active material, the chiral light360 is reflected as light with left-handed helicity, and the chirallight 355 is reflected as light with right-handed helicity.

Referring to FIG. 3B, examples of a directionally biased light-emittingdevice 391 that includes a light-collimating layer 394 is shown. Thedevice 391 includes a light-emitting layer 330, transparent substrate340, transparent cathode 350, transparent anode 365, top 380 and bottom390 as describe above with respect to the device 300 of FIG. 3B. Anoptically active reflective layer 392 is provided, which may in variousimplementations include the features described for an optically activereflective layer in other examples. A light-collimating layer 394 isdisposed between the light-emitting layer 330 and reflective layer 392,such that light 396 emitted at a relatively sharp angle may be deflectedwithin the light-collimating layer 394 to approach the reflective layer392 to a more moderate angle. The light thus reflected 398 may then exitthe device at the more moderate angle as well. This may allow thereflective layer 392 to have a wider effective angle and accommodate abroader field of view than otherwise allowed by the properties of thereflective layer 392 alone.

Referring to FIGS. 4A and 4B, examples of a directionally biasedlight-emitting device 400 that includes one optically active reflectivelayer 405 are shown. The device 400 includes a light-emitting layer 410formed on a substrate 420. The light-emitting layer 410 emits radiation440 that is circularly polarized and has a right-handed helicity. Asdiscussed with respect to FIGS. 5A and 5B, the helicity of the radiationemitted from the light-emitting layer 410 may be controlled by, forexample, introducing a population of spin up electrons into thelight-emitting layer 410. As shown in the example of FIG. 4A, theradiation 440 emitted from the light-emitting layer 410, which hasright-handed helicity, is reflected from the optically active reflectivelayer 405 and is emitted from a top 450 of the device 400. The opticallyactive reflective layer 405 has a reflection band that has aright-handed chirality, and, thus, because the radiation 440 is chirallight with right-handed helicity, the optically active reflective layer405 reflects the radiation 440. In some implementations, one or both ofthese layers 405, 410 may be pre-fabricated broad-band circularpolarization filters.

Referring to FIG. 4B, the behavior of the device 400 in the presence ofcircularly polarized light with left-handed helicity and right-handedhelicity is illustrated. Circularly polarized radiation 460 withright-handed helicity emanates from the device 400 and is reflected fromthe optically active reflective layer 405 as circularly polarizedradiation 460 with right-handed helicity. The polarized radiation 470 isreflected from the optically active reflective layer 405 because thechirality of the reflective band of the layer 405 is also right-handed.The radiation 470 is also reflected off of an object 465, changesorientation upon reflection to radiation 480, which has left-handedhelicity. Because the radiation 480 has left-handed helicity, thechirality of the reflective band of the optically active layer 405 doesnot match the chirality of the radiation 480. Thus, the radiation 480passes through the optically active reflective layer 405.

As discussed above, a TOUPLED may include one or more of an anode, anorganic light emitting layer, a cathode, a substrate, and an opticallyactive light blocking layer. In some implementations, the TOUPLED alsoincludes one or more of an electron transport layer (ETL), an electrontunneling barrier layer (TBL), and a hole transporting layer (HTL). Insome implementations, certain materials/substances may function as onediscrete element described above and herein or may act as more than onedescribed above and herein. For example, a particular material/substancemay be used as an anode and possess certain characteristics of a holetransport layer.

Referring to FIGS. 5A and 5B, examples of directionally biasedlight-emitting devices 500A and 500B that include an organiclight-emitting diode (OLED) stack are shown. Referring to FIG. 5A, thedevice 500A includes an OLED stack 20, a substrate 24, a right-handedoptically active reflective layer 28, and a left-handed optically activereflective layer 29. The OLED stack 20 includes a cathode 21, electrontunneling barrier layer 27, electron transport layer 25, light-emittinglayer 22, hole transport layer 26, and anode 23. Anode 23 is adjacent tothe substrate 24. Referring to FIG. 5B, the device 500B includes an OLEDstack 30, a substrate 34, and an optically active reflective layer 38.The OLED stack 30 of the TOUPLED may include a cathode 31, electrontunneling barrier layer 37, electron transport layer (ETL) 35,light-emitting layer 32, hole transport layer 36, and anode 33. Theanode 33 is adjacent to the substrate 34.

The directionally biased light-emitting devices 500A and 500B may beTOUPLEDs. TOUPLEDs may be considered as a series of adjacent layersconsecutively deposited on a substrate. The substrate may be thesubstrate 4, the substrate 204, the substrate 340, the substrate 24 orthe substrate 34 discussed above. Techniques for depositing layers onthe substrate include, for example, chemical vapor deposition, physicalvapor deposition, sputtering, thermal evaporation, e-beam deposition,vacuum deposition, spin-coating, and a modification of inkjet printertechnology. The techniques for depositing layers on the substrate alsomay be used to introduce or “dope” additional compounds into a layerthat has been deposited. For example, during fabrication of a TOUPLED,an electron transport layer (ETL), such as the electron transport layer25 or the electron transport layer 35 discussed with respect to FIGS. 5Aand 5B, may be deposited and doped with a metal either by depositing theETL on an ultra-thin layer of lithium or by depositing the ultra-thinlayer of lithium on the ETL. Based on the thicknesses of the layersprepared in this manner, the lithium may diffuse entirely, from eitherdirection, throughout the ETL, thus forming a degenerately-doped ETL. Alayer of lithium could also be deposited on both sides of the ETL, orthe lithium could be co-deposited with the ETL. The lithium layer may bedeposited such that the layer is about 0.5 to 1.0 nm thick.

The substrate on which the TOUPLED is fabricated is a material that istransparent to the chirality and wavelength of the radiation emittedfrom the TOUPLED. For example, the substrate may be glass and/orplastic. Polymer films made from, for example, polyvinylene chloride(PVC), polyethylene terephthalate (PET), polyether sulfone (PES),polyethylene naphthalate (PEN), polycarbonate (PC), nylon, polyetherether ketone (PEEK), polysulfone (PSF), polyether imide (PEI),polyarylate (PAR) and polybutylene terephthalate (PBT) may be used asplastic substrates.

The TOUPLED may include an anode, which injects positively chargedcarriers (“holes”) into a light-emitting layer. In some implementations,as mentioned above, depending on the particular type ofmaterial/substance utilized as an anode, the anode also may transportholes into the light-emitting layer. The anode may be made from, forexample, transparent indium tin oxide (ITO) or In₂O₃:SnO₂. The anode maybe, for example, the anode 23 or the anode 33 discussed above withrespect to FIGS. 5A and 5B respectively. The light-emitting layer may bethe light-emitting layer 22 or the light-emitting layer 32.

The TOUPLEDs also includes a cathode, such as the cathode 21 or thecathode 31. Cathodes inject negatively charged carriers or electronsinto the light-emitting layer. In some implementations, depending on theparticular type of material/substance utilized as a cathode, the cathodealso transports electrons into the light-emitting layer. Cathode layersmay be deposited using, for example, dc sputtering/cylindrical targetdeposition. ITO and Indium Zinc Oxide (IZO) are two examples of aconductive material for use in manufacturing transparent cathode layers.Subsequent cathode layers may include a transparent, metallic ornon-metallic materials and that serve to improve quantum efficiency ofthe emitting device, accommodate electron injection, minimize workfunction, and as a protective buffer layer facilitating the depositionof the ITO on predeposited organic layers; a transparent metal-dopedcathode layer that may also function as an exciton blocking layer and/oras a hole blocking layer; or a transparent, metallic or non-metalliccathode layer followed by an electron selective layer made of a materialthat possesses different conductivities for up and down electron spins.Suitable materials for use in transparent cathodes to facilitateelectron transport and injection may include, but are not limited to,lithium fluoride (LiF), aluminum (Al), litium-doped aluminum (Li:Al),magnesium-doped silver (Mg:Ag), bathocuproine (BCP)(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), cesium carbonate(CsCO3), lithium-doped bathocuproine (LiBCP) or cesium-dopedphenyldipyrenylphosphine oxide (CsPOP_(y2)).

In order to control the helicity of the chiral light emitted from theTOUPLED, the population of electrons having a spin up quantum spin stateas compared to the population of electrons having a spin down quantumspin state may be controlled. Electrons exist in two quantum spinstates, spin up and spin down, which are associated with equivalentunits of angular momentum values of opposite sign. A normallydistributed population of electrons is a mixture containing an equalnumber of electrons in the spin up state and in the spin down state.When a normally distributed population of electrons recombines withholes in a layer of organic light emitting molecules, chiral light(e.g., circularly and/or elliptically polarized light) is produced. Thelight emitted is approximately an equal mixture of light with righthanded helicity (RH) and light with left handed helicity (LH).

In some implementations, however, the TOUPLED may utilize electrons in asingle spin state. When the electrons in a single spin state recombinewith holes in the TOUPLED, due to quantum spin-selection rules, theemitted chiral light has a single handedness (helicity) relative to theemitter molecule orientation. The helicity of the emitted light ismeasured with respect to the emitter molecule's axis of magneticalignment and the sign is a function of the spin state of the injectedelectrons and holes. For example, when electrons in the spin-up staterecombine with holes, chiral light with right-handed helicity is emittedin a forward direction with respect to an aligning magnetic field. Whenelectrons in the spin down state recombine with holes, chiral light withleft-handed helicity is emitted in a forward direction with respect toan aligning magnetic field.

Spin polarized electrons may be produced by, for example, spinfiltration via tunneling and spin polarization via a magnetizedinjector. Spin filtration via tunneling utilizes an electron tunnelingbarrier layer (TBL) located either adjacent to the cathode or sandwichedbetween two electron transport layers, one of which is adjacent to thecathode. Electrons in the spin up state have greater momentum thanelectrons in the spin down state. The greater momentum of electrons inthe spin up state allows these electrons to tunnel through the TBL,while electrons in the spin down state are unable to pass through theTBL. Therefore, the TBL enriches the current flowing in thelight-emitting layer with electrons in the spin up state. The populationof spin up electrons radiatively recombines with holes in thelight-emitting layer, and, thus, the light-emitting layer emits chirallight with right handed helicity. Spin tunneling filtration may yield anelectron population with nearly 100% spin up electrons. Thus, theemitted radiation is nearly 100% right-handed polarized radiation. TheTBL may be made from, for example, Eu_(x)O_(y) (x>>y), which is selectedfor its ability to participate in large exchange splitting in theconduction band (on the order of 0.6 eV), and because of its high degreeof transparency. Other materials having a high degree of transparencyand the ability of participate in exchange splitting, such as magnesiummonoxide and ITO, may be used. Electrons carry different magneticmomentum depending on the spin state of the electron. Certain materialsparticipate in exchange splitting, and in these materials, electrons inthe spin-up state (which have a higher momentum that electrons in thespin-down state) have a higher probability of tunneling through thematerial. The larger the exchange splitting, the more effectively thematerial discriminates between spin-up and spin-down electrons. Thus, inmaterials having relatively large exchange splitting, spin- up electronshave a higher probability of tunneling through the material and, as aresult, more spin-up electrons pass through. As a result, aspin-polarized current is generated.

In some implementations, electrons in the spin up state may be producedvia a magnetized injector. A magnetic electron injection cathode, suchas chromium doped indium tin oxide, forms spin-up polarized electronsthat are injected into the light-emitting layer. The radiativerecombination of electrons in the spin-up state with holes results inthe emission of chiral light with right-handed helicity. Theelectron-spin selective cathode may be made from, for example, chromiumdoped indium tin oxide (Cr:ITO); chromium doped indium oxide (Cr:IO);any transparent half metal (Mo, Zr, Nb, Ru, Tc doped with K₂S (about 5%doped)); Zr, Tc, and Ru doped with K₂O (about 5% doped); or Zr, Nb, andRu doped with K₂Se, K₂Te, or Rb₂S; any transparent Heusler alloy; anycompound from a class of materials known to be half-metallic and havingthe formula X₂YZ, where X and Y are transition elements (groups IB toVIIIB on the periodic table) and Z is a group III, IV, or V element.

In some implementations, a magnetized injector may be used incombination with an electron tunneling barrier layer to achieve a purerspin-polarized current at a higher ambient temperature than either thespin filtration or the magnetized injector may achieve singly. Themagnetized injector may be used to supply a pre-spin polarized current(e.g., spin-up) to the tunnel barrier that in turn filters out anyremaining electrons in the spin down state. Polarized electrons in thespin up state also may be produced by hybrid spin injecting tunnelingfilters. Like their electron counterparts, holes may be considered asexisting in two separate quantum spin states. Thus, chiral light of asingle helicity may be produced by the radiative recombination ofelectrons with spin polarized holes. Chiral light of a single helicityalso may be produced by the radiative recombination of spin polarizedelectrons with spin polarized holes. FIG. 6A shows an example of adirectionally biased light-emitting device that includes an organiclight-emitting diode (OLED) stack. The example device 600 shown in FIG.6A is a TOUPLED that includes an organic light-emitting layer (OLEL) 602that is transparent. The OLEL 602 includes a cathode 604, an electroninjection layer 606, an electron transport layer 608, an organiclight-emitting layer 610, a hole transport layer 612, and an anode 614.An optically active reflective layer may be disposed on either thecathode or the anode of the stack. In the example shown in FIG. 6A, anoptically active reflective layer 630 is disposed on the cathode 604.

In the example shown in FIG. 6A, the anode 614 includes a conductiveanode of ITO and glass. The ITO layer is approximately forty-twonanometers (42-nm) thick. The light-emitting layers 602 also include ainter-layer electrical short reduction layer 613 made from a layer ofmolybdenum oxide (MoO3) that is about 20-nm thick, and the holetransport layer 612, which in this example includes a layer of N,N′di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB) that is about 55-nmthick. The light-emitting layer 610 is made of Alq3+C6 and is about60-nm thick, and the electron transport layer 608 is about 40-nm thickand is made of 4,7-Diphenyl-1,10-phenanthroline (Bphen). The electroninjection layer 606 is about 0.5-nm thick and made of lithium fluoride(LiF). In the example of FIG. 6A, the cathode 604 includes ITO andaluminum (Al). The ITO layer is about 65-nm thick, and the aluminumlayer is about 100 nm thick. The presence of the aluminum layer allowsthe ITO to be sputtered, or otherwise, applied to the electron injectionlayer 606.

In another implementation, the cathode may include a conductive cathodeof ITO and glass, an electron injection layer of cesium carbonate(CsCO3), an electron transport layer of Bphen, a light-emitting layer ofAlq3+C6, a hole transport layer of MoO3 and NPB, and an anode of silver(Ag) and ITO. The silver portion of the anode may be a thin layer ofsilver through which light passes, and the silver acts as a protectivelayer that allows the ITO to be sputtered onto the hole transport layer.

The device 600 also includes the optically active reflective layers 630.The optically active reflective layers 630 include a layer of glass 632,and an alignment coating 634 that is about 30-40-nm thick and buffedhorizontally. A layer of the alignment coating 634 is placed on bothsides of a right-handed GLC 636, which is about 8-μm thick, and a layerof glass 638 is disposed on the opposite side of the GLC 636. An indexmatching adhesive 640 is disposed on the layer of glass 638, and analignment coating 646 that is buffed vertically and is about 30 to 40-nmthick is disposed on both sides of a left-handed GLC 648 that is about8-μm thick. A layer of glass 652 and an index matching adhesive layer654 are also included in the optically active reflective layers 630. Inthe example shown in FIG. 6A, the right-handed GLC and the left-handedGLC are both tuned to have a reflection band about 75-nm wide andcentered at 525-nm.

In either of these implementations, the optically active layers 630 maybe adjacent to the cathode 604 or to the anode 614. In the example ofFIG. 6A, the optically active layers 630 are adjacent to the cathode 604and the directionally biased light from the device 600 is emitted fromthe bottom 650 of the device.

The layer thicknesses may be other than specified in the example of FIG.6A. In some implementations, the hole transport layer 612 may be athickness between 5-nm and 100-nm, the organic light-emitting layer 610may have a thickness between 10-nm and several hundred nm, the electrontransport layer 608 may have a thickness between 10-nm and severalhundred nm, and the thin-metal electron injection layer 606 (which isaluminum in the example of FIG. 6A), may have a thickness between 10-nmand several hundred nm.

FIG. 6B illustrates emission characteristics of the device 600 that isshown in FIG. 6A. The emission characteristics include a curve 690 and acurve 695, each of which represent intensity as a function of thewavelength (in nm) of radiation emitted from the device 600. The curve690 shows emissions from the bottom of the device 600, and the curve 695shows emissions from the top of the device 600. As seen in FIG. 6B, thedevice 600 is directionally biased such that the intensity of emissionsfrom the bottom of the device 600 is greater than the emission from thetop of the device 600. The emissions from the top of the device 600 aremainly attributable to leakage from the device 600. However, theemissions from the bottom of the device 600 are caused by reflections ofthe light from the light emitting layers 602 off of the optically activelayers 630. Thus, the emissions from the bottom of the device 600 aresignificantly greater in intensity than the emissions from the top ofthe device 600, and the emissions from the bottom of the device 600 arecentered on a wavelength of about 525 nm due to the tuning of thereflection bands of the GLC layers 636 and 648 that are included in theoptically active reflective layers 630.

In addition to the tuning of the reflection bands as a function ofwavelength, some applications may benefit from the optically activereflective layer selectively reflecting light emitted within aparticular field of view. Therefore, in some implementations, theoptically active reflective layer may also be tuned according to angleof incidence of radiation. Different reflective layers, as describedfurther below, may have a tuned angle of reflection using differentmethods known in the art; for example, the angles of the beams usedduring fabrication in irradiating reflective layers may affect theresulting field of view.

In some implementations, the TOUPLED also may include additional layersdisposed between the anode and the cathode, each layer having differentcompositions and performing different functions. Such materials shouldbe selected for their charge mobility characteristics to generate smoothenergy-level transitions (ionization potentials) between successivelayer interfaces where unrestricted charge transport is desired or togenerate energy barriers where localization of charge carrierrecombination is desired. Materials may be small molecules or polymers.For example, the TOUPLED may include an electron transport layer (ETL),such as the electron transport layer 35. The ETL may efficientlydisperse the injected current of negative charge carriers (electrons)across the surface of the layer, and the ETL provides a homogenouscurrent at the boundary of the ETL and the layer on the side of the ETLopposite from the cathode. The ETL may also serve as a positive chargecarrier (hole) blocking layer to promote the likelihood and localizationof charge carrier recombination in the light emitting layer. Aspin-polarized electron transport layer may improve the probability thatthe spin polarized state of the injected electrons is conserved.Suitable ETL materials include, but are not limited to4,7-Diphenyl-1,10-phenanthroline (Bphen),2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), orTris-(8-hydroxyquinolinato)aluminum (Alq₃).

In other implementations, a hole transport layer (HTL), such as the holetransport layer 36, may be provided to efficiently disperse the positivecharge carriers (holes) across the HTL so that a homogenous current(hole) is provided to the surface of the layer adjacent to the HTL,which may be the light-emitting layer. The HTL may also serve as anegative charge carrier (electron) blocking layer to promote thelikelihood and localization of charge carrier recombination in the lightemitting layer. One or more HTL layers may be used in succession. TheHTL may be made from a host of materials including but not limited toN,N′ di(naphthalene-1-yl)-N,N′-diphenyl-benzidine (NPB), or4,4′-bis[N(1-napthyl)-N-phenylamino]biphenyl (alpha-NPD) (NPD),1,3,5-Tris(diphenylamino)benzene 97% (TDAB), or from the TDATA familysuch as 4,4′,4″-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA) assmall molecule examples, or Poly(2-vinylnaphthalene) as a polymerexample. Dopant materials may be added to the HTL to improve devicelifetime and efficiency. For instance, NPB may be doped with molybdenumoxide (MoO3) to reduce the hole injection barrier, improve interfacialstability, and suppress crystallization of the HTL.

In some implementations, the materials/substances that function as theETL or as the HTL may include the same materials that are incorporatedinto the light-emitting layer to produce the electroluminescentemission. If the HTL or ETL function as the emissive layer (e.g., thelight-emitting layer) of such a device, then the TOUPLED may be referredto as having a single heterostructure. Alternatively, a TOUPLED, havinga separate layer of electroluminescent material included between the HTLand ETL, may be referred to as having a double heterostructure. Thus, aheterostructure for producing electroluminescence may be fabricated as asingle heterostructure or as a double heterostructure.

In some implementations, one or more buffer layers may be insertedbetween successive layers to reduce the abrupt differential barrierheight between successive layer work-functions.

In some implementations, a light-collimating layer may be disposedbetween the light-emitting layer and the optically active reflectivelayer in order to collimate the emitted light and reduce its angle ofemission. For example, a light-collimating layer may limit the directionof radiation emission to an angle less than 40 degrees from normalrelative to the surface of the device. The light-collimating layer mayhelp to direct the light to within the light-emitting envelope, and maybe used in conjunction with angle tuning of the radiation emittinglayer. In some implementations, the light-collimating function may beperformed by one or more substrates, and may be a feature of thesubstrates 204, 340, or 420 as described above.

The material properties of the light-emitting layer determine thewavelength and, hence, the color of the radiation emitted from the OLED.Through selecting differing organic solids for the light-emitting layerwith a material such as coumarin 6 (C6), or through doping the organicsolid used to make the light-emitting layer, the color of the radiationemitted may be varied. In some implementations, individual TOUPLEDstacks include light-emitting layers that emit light of a particularcolor, and in other implementations, a TOUPLED includes multiplelight-emitting layers that each emit light of different colors. TOUPLEDlight emitting materials with narrow band emission (saturated color)should be selected Suitable material for the light emitting layerinclude, but are not limited to Tris-(8-hydroxyquinolinato)aluminum(Alq₃), Bis-(8-hydroxyquinolinato)zinc (Znq),Tris(1,10-phenanthroline)ruthenium(II) chloride hydrate, as smallmolecule examples, orPoly(9,9-di-(2-ethylhexyl)-9H-fluorene-2,7-vinylene) as a polymerexample.

Furthermore, in some implementations, the wavelength of the radiationemitted by the organic light emitting layer (OLEL) may be modified byaddition of fluorescent and/or phosphorescent materials that absorb thelight emitted by the light-emitting layer and re-emit radiation oflonger wavelength. In some implementations, the color of the emittedradiation may be altered by placing a colored or photoluminescent filmbetween the TOUPLED and the observer.

The TOUPLED also includes an optically active reflective layer, such asthe optically active reflective layer 2, the optically active reflectivelayer 202, the optically active reflective layers 405 and 420, theoptically active reflective layer 28 and 29, or the optically activereflective layer 38. The optically active reflective area may be anoptically-active chiral-light blocking layer (OA-LBL). Materialssuitable for use as OA-LBLs include, for example, dichroic materials,organic compounds containing asymmetric carbon atoms, and from inorganiccompounds such as glass-forming chiral nematic liquid crystals (GLC),chiral dielectric sculptured thin film, and holographic opticalrecording material wavelength selective reflectors. Furthermore, thelayers that function as OA-LBL may be deposited using methods similar tothose used to deposit the other layers of a TOUPLED. Sculptured thinfilms are fabricated using a technique that involves controlling themotion of the substrate on which the film is fabricated during thefabrication process. Typically, fabrication of the sculptured thin filminvolves computerized control of the rotation of the substrate about twoaxes during the deposition process. The holographic optical recordingmaterial is a material suitable for holographic recording and thereforereflecting the wavelength, polarization, and incident angle of lightwith properties matching the properties of light emitted from thelight-emitting layer. Suitable materials facilitate the recording ofmultiplexed holographic images of light incident at multiple angles,which enable the OA-LBL to reflect emitted light over a wide field ofview. In implementations comprising two OA-LBLs, a standardpre-fabricated broad-band circular polarization film consisting ofquarter-wave retardation and linear polarization sublayers may serve asa suitable OA-LBL, so long as the circular polarization film isdeposited between the light emitting layer and the second OA-LBL. Such aconfiguration may be used in applications where it is desired to reducethe color tint that inherently results from narrow-band OA-LBLreflection of ambient light.

In one implementation, the OA-LBL may include a GLC layer which is acholesteric thin film including a helical stack of quasinematic liquidcrystal layers. The optical properties of the GLC film are determined toa large degree by the chirality (i.e. right- or left-handedness) andhelical pitch length. The chirality of the GLC film is determined by therotational direction of the cumulative nematic director twisting whichresults from the rotation of each successive quasinematic liquid crystallayer about the intended optical axis of the film. The helical pitchlength determines the distance required to complete a 360-degreerotation of the optical director. A cholesteric liquid crystal film maybe made of a helical stack of quasinematic layers, and the handedness(right-handedness or left-handedness) describes the direction in whichtwisting of the nematic director occurs from one layer to the next. Thehelical pitch length is the distance along the direction of propagationof radiation through the layers over which the director rotates 360°.

Cholesteric liquid crystals may be derived from nematic liquid crystalsthat have been doped with very low concentrations of chiral dopants, andthe cholesteric pitch of the cholesteric phases is sensitive tostructural modifications of the chiral dopant. Thus, the initial helicalpitch is largely determined by the selection of a particular chiraldopant, and the reflection band of the GLC layer may be set by selectinga particular dopant molecule without necessarily performing subsequentphotomodulation on the GLC layer. The ability of the GLC film toselectively reflect a given wavelength is governed a relationshipbetween the helical pitch length and the extraordinary and ordinaryrefractive indices of the quasi-nematic layers. The differential betweenthese extraordinary and ordinary refractive indices determines theoverall optical birefringence of the GLC film, which, in turn,determines the width of the selective reflection wavelength band. Thewavelengths associated with this selective reflection band may bealtered by modifying the GLC chemical composition. Additionally oralternatively, the reflection band may be tuned by, for example,photomodulation of the GLC film or by altering or adjusting themolecular ratio of the GLC film. In some implementations, the reflectionband may be adjusted using both photomodulation and adjustment of themolecular ratio by, for example, adjusting the molecular ratio of thematerials in the GLC film and then photomodulating the GLC film.

In some implementations, the reflection band of the GLC layer may beconsidered to act as an optical notch filter that has a reflection bandset (or tuned) by adjusting a molecular ratio between the materials fromwhich the GLC film is made. For example, the GLC optical notch filtermay have two adjacent single-handed GLC films, with each film having achirality that is opposite from the chirality of the other film. In thisimplementation, each GLC film includes an appropriate ratio ofright-handed (R) and left-handed (S) glassy cholesteric material suchas, for example, 2N1CH-R and 2N1CH-S, respectively. A ratio of theleft-handed glassy cholesteric material to the right-handed glassycholesteric material may be adjusted to tune the reflection band of theGLC film. This ratio may be referred to as the GLC ratio and may beconsidered to be a molecular ratio of the right-handed (R) glassycholesteric material to the left-handed (S) glassy cholesteric material.For example, a GLC ratio of S-to-R molecules of 81:19 results in anenantiomeric excess of “S” molecules that yields a single left-handedfilm in a particular wavelength range. The opposite GLC ratio (S-to-R of19:81) results in an enantiomeric excess of “R” molecules that yields asingle right-handed film at the same, or almost the same, wavelengthrange. Adjusting the GLC ratio shifts the reflection band of the GLCfilm, and may thus be considered to tune the GLC film. Additionally, themolecular composition of the glassy cholesteric material may be modifiedto adjust the width of the optical notch (e.g., the spectral width ofthe reflection band). An example structure of a GLC molecule from U.S.Pat. No. 7,001,648, which is herein incorporated by reference in itsentirety, as shown below.

In implementations having multiple GLC films, the GLC films may beadjacent to each other by overlapping, or partially overlapping, eachother such that radiation that is incident on one of the GLC films andpropagates through the GLC film is also incident on the other GLC film.The adjacent GLC films may overlap by making contact with each other, orthe GLC films may be positioned close to each other, without necessarilytouching each other, such that radiation passes from one film to theother. The GLC films may be aligned such that the optical director ofone GLC film is perpendicular to the optical director of the other GLCfilm.

In some implementations, the GLC reflection band wavelength may beincreased or decreased by completing a photomodulation process on adeposited GLC film. In some implementations, the photomodulation processincludes heating the GLC thin film to a point above the glass transitiontemperature of the film (Tg) followed by a period of irradiation withultraviolet (UV) radiation. The glass transition temperature of the filmdepends on the chemical composition of the film. The GLC thin film alsomay be heated to a temperature near a critical temperature (Tc) of thefilm. For example, a GLC with Tg of 68° C. and Tc of 134° C. may beheated to 120° C. (thus the GLC thin film is heated to a temperaturethat is 14° C. from the Tc). The heating is followed by a period of UVirradiation with, for example, UV radiation having a wavelength of 334nm and an intensity of 70 mW/cm². The angle of the irradiation may, insome implementations, impact the resulting angle at which the GLC thinfilm can reflect the selective reflection band; it may therefore bepossible to tune the field of view of the resulting optically activereflective layer by selecting the angle of irradiation in addition toother factors used to select a particular reflection band.

The longer the exposure time to the UV radiation, the longer theresulting nematic liquid crystal helical pitch length, and hence thelonger the selective reflection band wavelength of the GLC thin film.The irradiation time is dependant on the initial (unmodulated)reflection band, but the irradiation time is a time duration that issufficient to alter the reflection wavelength band of the GLC thin film.The closer the initial reflection band is to the final desiredreflection band, the shorter the required irradiation. Typically, withinthe visible spectrum, irradiation times may last from tens of seconds,to tens of minutes. For example, the irradiation time to shift thereflection band from 400 nm to 550 nm may be about 10 minutes, whereasthe band shift from 400 nm to 750 nm may be about 40 minutes. Theradiation used to irradiate the GLC film may be unpolarized UV light. UVlight is used if only a GLC optical notch filters (stacked left- andright-handed GLC filters) are being simultaneously photomodulated (e.g.,tuned).

The film is then cooled to a point below (Tg; typically roomtemperature) at which point the attained selective reflection wavelengthbecomes frozen in the solid state of the GLC thin film.

In some GLC materials the photomodulation process is reversible, whereheating of the GLC thin film with a predetermined selective reflectionband above (Tg) followed by irradiation of the film with a shorterwavelength than the selective reflection band for a sufficient period oftime decreases the helical pitch length of the nematic liquid crystal,thereby decreasing the wavelength of the GLC selective reflection band.Subsequent cooling to a point below Tg will freeze the reflectionwavelength in the solid state of the GLC thin film. In the TOUPLEDapplication, in one implementation, a GLC OA-LBL layer of a givenchirality (left- or right-handed) is selected to match the chirality ofthe helically-polarized light emitting layer and is deposited on theexposed side of the TOUPLED substrate. The GLC layer is subsequentlyphotomodulated (e.g., tuned) to encompass the wavelength band emitted bythe organic light-emitting layer. The photomodulation process may beaccomplished by using either an external radiation source or lightemitted by the TOUPLED light emitting layer itself.

In another implementation, the TOUPLED light emitting layer includes alight emitting layer that achieves a less than ideal degree of helicalpolarized emission. In this implementation, a GLC OA-LBL layer ofright-handed chirality and a GLC OA-LBL layer of left-handed chiralityare deposited successively on the exposed side of the TOUPLED substrate.Following deposition, both layers are subjected to an identicalphotomodulation process to tune the GLC OA-LBL layers to encompass thewavelength band emitted by the organic light-emitting layer. Thephotomodulation process may be accomplished by using either an externalradiation source or light emitted by the TOUPLED light emitting layeritself. Chiral light with a right handed helicity may be reflected bythe right-handed OA-LBL and chiral light with left handed helicity maybe reflected by the left-handed OA-LBL. Electrons in the spin-up stateproduce a chiral light wave with right handed helicity, that in turn maybe reflected by the right-handed OA-LBL. The result is a transparentdevice that emits chiral light only from that side of the device thatdoes not have the OA-LBL layer or layers.

In some implementations, the OA-LBL may include a holographic opticalrecording material layer which is irradiated to form a multiplexedholographic notch filter. The holographic optical recording materiallayer may be irradiated with multiple collimated object beams which arecircularly polarized and have a common chirality. The beams areprojected at a series of angles, and successively interfere with acommon collimated reference beam to generate several multiplexedreflection holograms in the recording material layer. Both thewavelength and series of angles of the beams are chosen to create amultiplexed hologram that efficiently reflects radiation over thedesired field of view at wavelengths within the emission band of theTOUPLED light emitting layer.

Ambient light is randomly polarized and includes a combination ofwaveforms polarized in all orientations. The majority of ambient lightis of a wavelength that is outside of the OA-LBL stop band (which alsomay be referred to as the reflection band) and is therefore transmittedby the OA-LBL layer. The relatively small portion of ambient light thatfalls into the OA-LBL stop band and that also matches the chirality ofthe OA-LBL is reflected. Chiral light produced within the TOUPLED from apopulation of electrons in the spin up state, for example, may beemitted from the top of the device and absorbed or reflected by theOA-LBL on the bottom of the device. In contrast, the device is equallytransparent to ambient light passing through the device in eitherdirection.

Referring to FIG. 7, an example process 700 for fabricating adirectionally biased light emitting device is shown. The polarized lightemitting device may be a TOUPLED as discussed above. Aradiation-emitting layer is formed (710). The radiation-emitting layerincludes a radiation-emitting material is disposed between a transparentanode and a transparent cathode. The radiation-emitting material has aspectral emission band such that all radiation, or almost all radiation,emitted from the radiation-emitting material has a wavelength that fallswithin the emission band. The emission band of the radiation-emittingmaterial depends on properties, such as index of refraction, of thematerial from which the radiation-emitting layer is made. Theradiation-emitting material may be a light-emitting layer made from anorganic material such as, for example, Alq3+C6. The radiation-emittingmaterial may be a light-emitting layer such as the light-emitting layers7, 201, 330, 410, 22, and 32 discussed above.

Typical radiation emission layers emit light in a uniform Lambertiandistribution—light emitting evenly in all directions about the source.Ideally, the OA-LBLs correspondingly block light in a Lambertian manner.However, many less expensive OA-LBLs are only capable of reflectinglight that is incident in an envelope of limited angle, for example,angles of less than 40 degrees. To enhance performance of less expensiveOA-LBLs, an optional prefabricated light-collimating layer may bedeposited between the radiation emitting layer and the OA-LBL. Materialssuitable for use as light collimating layers include, for example,photonic crystal composites designed for narrow or wide-bandcollimation, and micro-louver films such as the Vikuiti Light ControlFilms available through 3M Corporation.

An optically active reflective layer is deposited adjacent to theradiation-emitting layer (720). Thus, the optically active reflectivelayer may be on the anode side or the cathode side of theradiation-emitting layer. The optically active reflective layer mayinclude glass-forming chiral nematic liquid crystals, and the opticallyactive reflective layer has a spectral reflection band that may bereferred to as the reflection wavelength band. The optically activereflective layer reflects radiation that has a wavelength within thereflection band. The optically active reflection layer transmits little,if any, radiation that has a wavelength in the reflection band andpossesses the same chirality as the optically active reflection layer(because the optically active reflection layer reflects such radiation).The optically active reflective layer may be deposited on a transparentsubstrate such as the transparent substrates 4, 204, 340, 420, 24, and34 discussed above. The transparent substrate may be located between theoptically active layer and the radiation-emitting layer, but that is notnecessarily the case. The optically active reflective layer may includea first glassy liquid crystal (GLC) film made of a right-handed materialand a second GLC film made of a left-handed material that is adjacent tothe first GLC film.

The reflection wavelength band of the optically active reflective layeris adjusted to at least partially encompass the emission wavelength bandof the radiation-emitting layer (730). Thus, after the reflectionwavelength band of the optically active layer is adjusted, the opticallyactive layer reflects radiation that is emitted from theradiation-emitting layer. However, because the layers of the device aretransparent to ambient light, a user of the device is able to seethrough the device. Thus, as discussed below, the device may be used forin-line-of-sight illumination applications. As discussed above,adjusting the optically active reflection layer may includephotomodulating the optically active reflection layer, adjusting themolecular composition of the optically active layer, or photomodulatingthe optically active layer after adjusting the molecular composition ofthe optically active layer. Some implementations where a broad-bandcircular polarization film is used may not require any opticaladjustment steps during fabrication of the device, because the filmalready possesses established optical properties.

A second optically active layer may be deposited on the optically activelayer deposited in (720). The second optically active layer has achirality that is opposite that of the optically active layer depositedearlier. Thus, if the earlier-deposited optically active layer has aleft-handed chirality, the second optically active layer has aright-handed chirality. The reflection wavelength band of the secondoptically active layer may be adjusted separately from the firstoptically active reflection band and adjusted on a separate substrate.Once the reflection band of the second optically active layer isadjusted, the second optically active layer may be bonded to one side ofthe TOUPLED device.

The directionally biased transparent light-emitting devices discussedabove such as devices 200, 300, 400, 500A, 500B, and 600 may be used inan electronic display, in-line-of-sight illumination applications, andin dual-sided transparent display applications. For example, the devicesmay be used in a non-transparent flat panel display and standardapplications of flat panel displays, and the devices may be used intransparent flat panel electronic displays including active matrix-baseddisplays having a thin film transistor (TFT) backplane, passivematrix-based displays, monochrome displays, or full-color displays. Touse the device in an electronic display, the GLC layer may be pixilatedsuch that portions of the GLC layer are individually addressable.

To use the light-emitting device in an monochrome display, a singleoptically active layer (e.g., a GLC or sculptured thin film) that isshared by all, or multiple, pixels that make up the display) may beused. For full-color displays in which sets of red, green, and bluepixels are arranged in a spatial pattern and used to make a multi-colordisplay, the reflection band of various portions of the GLC layer may beselectively tuned by exposing the various portions of the GLC layer tophotomodulation. In this manner, the GLC may be considered to bepixilated.

FIGS. 8A-8C illustrate a process for pixilating a GLC, or otherphototunable optically active material.

Referring to FIG. 8A, a red-light emitting layer 810, a green-lightemitting layer 812, and a blue-light emitting layer 814 are deposited ona glass substrate 820. Each of the red-light emitting layer 810, thegreen-light emitting layer 812, and the blue-light emitting layer 814may be OLEDs that emit, respectively, red light, green light, and bluelight. A phototunable optically active reflective layer 825 is disposedon the emitting layers 810, 812, and 814.

Referring to FIG. 8B, a shadow mask 830 having openings 832 and 834 ispositioned above the phototunable optically active reflective layer 825.The openings 832 and 834 are sized to correspond to a size of a pixel tobe formed on the optically active reflection layer 825. UV radiation 840is directed towards the shadow mask 825 and passes through the openings832 and 834 to irradiate portions 826 and 827, respectively, of theoptically active reflecting layer 825. The portions 826 and 827 areexposed to the UV radiation 840 for a sufficient amount of time to tunethe reflection band of the portions 826 and 827 such that the portions826 and 827 reflect red light having a helicity that is the same as thatof the layer 825. Subsequently, the shadow mask 830 may be repositioned(not shown) relative to the optically active layer 825 such that otherportions of the optically active reflective layer 825 are exposed to theUV radiation 840. As a result, the reflection band of each of theseportions is tuned to reflect red, green, or blue light depending on thetime duration of the exposure the UV radiation 840.

Referring to FIG. 8C, the localized irradiation of the optically activereflecting layer 825 has been repeated to produce, in addition toportions 826 and 827, portions 832, which reflect green light, andportions 834, which reflect blue light. Thus, the optically activereflecting layer 825 has been pixilated into portions (which may bepixels) that reflect red light, portions that reflect green light, andportions that reflect blue light. As a result, light emitted from thelight-emitting layers 810, 812, and 814 is reflected from, respectively,the portions 832, 827, and 834 of the optically active reflective layer825 and passes through the transparent substrate 820.

Thus, FIGS. 8A-8C illustrate a process for pixilating an opticallyactive reflective layer, such as a GLC. However, for applications inwhich maximization of transmission of ambient light is not a priority,instead of pixilating an optically active reflective layer intoindividual pixels or portions having individually tailored reflectionbands, the optically active layer may be deposited in a continuousstrip, strips, or sheet that spans the entire height and/or width, or aportion of the height or width, of the emitting device. Configurationsthat use a single, non-pixilated optically active reflective layer maybe simpler and/or less expensive to manufacture than an implementationthat includes a pixilated GLC.

FIGS. 9A-11A each illustrate a perspective view of an exampleconfiguration of a directionally biased light-emitting device thatincludes multiple single optically active reflective layers. FIGS.9B-11B, respectively, show a side-view of a vertical cross-section ofthe configurations shown in FIGS. 9A-11A.

Referring to FIG. 9A, a directionally biased light-emitting device 910includes pixels 915, a transparent substrate 920, an optically activelayer 925 with a reflection band tuned to reflect red light, anoptically active layer 930 with a reflection band tuned to reflect greenlight, and an optically active layer 935 with a reflection band tuned toreflect blue light. The pixels 915 may be OLEDs that preferentially emitlight from the bottom (the side in contact with the transparentsubstrate 920), and each of the optically active reflective layers 925,930, 935 are shared among all pixels 915. The optically activereflection layers 925, 930, and 935 may be arranged in a differentorder, such as shown in FIGS. 10A and 11A.

In operation, the pixels 915 are transparent to light and are, thus,able to emit light from both sides (e.g., from the top and bottom of thepixel). However, the light emitted by the pixels 915 is preferentiallyemitted towards the bottom of the pixel (e.g., toward the transparentsubstrate 920). Light that is emitted from the bottom of the pixelpasses through the transparent substrate 920 and is reflected from oneof the layers 925, 930, 935 that has a reflection band that includes thewavelength and chirality of the light emitted from the pixel. Forexample, pixel 918 emits blue light that passes from the bottom of thepixel 918 through the substrate 925 and through the red layer 925. Thelight is then reflected from the blue layer 930 and exits through thetop of the pixel 918 as blue light. The blue light from the pixel 918does not reach the green layer 935. The pixel 919 emits green light thatfrom the bottom of the pixel 919. The emitted light passes through thered optically active layer 925 and the blue optically active layer 930before the light is reflected from the green optically active layer 935.The reflected light is transmitted by the blue optically active layer930, the red optically active layer 925, the substrate 920, and thepixel 919 to exit the display 910A as green light. The pixel 917 emitsred light into the transparent substrate 920, and the light is reflectedfrom the red optically active layer 925 and exits the device 910 as redlight.

Referring to FIG. 9B, a side view of a vertical cross-section of thedevice 910 taken along the line “A” is shown. As shown in FIG. 9B, eachof the optically active layers 925, 930, and 935 are under the pixels917, 918, 919. Although not shown, the optically active layers 925, 930,and 935 are also under the remaining pixels 915.

Referring to FIG. 10A shows a perspective view of a directionally biasedlight-emitting device 1010. The display device 1010 is similar to thedevice 910 except that the pixels 915 are deposited on the opticallyactive layers 925, 930, and 935 rather than on the transparent substrate920. In the implementation shown in FIG. 10A, the optically activelayers 925, 930, and 935 are deposited on the transparent substrate 920.Thus, in this implementation, light emitted from the bottom of the pixel918 is reflected off of the blue optically active layer 930 withoutpassing through the transparent substrate 920. This implementation mayresult in improved performance (e.g., increased brightness from thedevice 1010) because of, for example, reduction in losses caused bylight passing through the substrate 920 as the light passes from thepixels 915 to the appropriate optically active layer.

FIG. 10B shows a side-view of a vertical cross-section of the device1010 taken along the line “B”.

FIG. 11A shows a perspective view of a directionally biasedlight-emitting device 1100. In the device 1100, the pixels 915 aredeposited on the substrate 920, and the optically active reflectivelayers 925, 930, 935 are bonded to the pixels 915. In thisimplementation, the optically active reflective layers are formed on aseparate substrate, tuned such that their respective reflection bandsreflect red, green, or blue light, and then bonded to the pixels 915. Inthis implementation, light is preferentially emitted from the top of thepixels 915, reflects off of the appropriate optically active layer,passes through the pixels 915 again, and exits the device 1100 throughthe transparent substrate 920. In such a design, the substrate 520 mayprovide protection for the pixels 915 as well as a platform fordeposition. FIG. 11B shows a side view of a vertical cross-section ofthe device 1100 taken along the line “C”.

In the examples shown in FIGS. 9A-11A, the pixels 915 are arranged in adelta configuration in which pixels that emit a particular color arearranged along diagonal lines. However, the pixels 915 may be arrangedin other configurations that are suitable for RGB displays. For example,the pixels 915 may be arranged in a striped pattern that includesalternating contiguous segments of red-light emitters, green-lightemitters, and blue-light emitters. In another example, the pixels 915may be arranged in a mosaic pattern, or a Pentile® pattern. The Pentile®pattern is available from Samsung Electronics Co., LTD. of the Republicof Korea.

Referring to FIG. 12, a stacked transparent light-emitting device isshown. A single pixel, or emitting layer, 1200 is deposited on atransparent substrate 1205. The pixel 1200 includes a blue-lightemitting layer 1210, an optically active reflective layer 1215 thatreflects blue light, a green-light emitting layer 1220, an opticallyactive reflective layer 1225 that reflects green light, and a red-lightemitting layer 1230, an optically active reflective layer 1235 thatreflects red light. In the implementation shown in FIG. 12, each of thelight-emitting layers 1210, 1220, and 1230 are associated with atransparent anode (not shown) and a transparent cathode (not shown) thatcontrols the emission of light from each of the light-emitting layers.

The implementation shown in FIG. 12 is different from those shown inFIGS. 9A-11A because each of the light-emitting layers in device 1200has a corresponding optically active reflection layer that is adjacentto the emitting layer. Thus, in device 1200, light emitted from one ofthe light-emitting layers is reflected from the adjacent layer insteadof traveling through multiple layers as may be the case in theimplementations shown in FIGS. 9A-11A. As a result, improved performance(e.g., greater intensity of light emitted from the top of the device1200) may be realized due to the minimization of waveguiding.

Referring to FIG. 13, a TOUPLED as a stacked transparent light-emittingdevice is shown. FIG. 13 shows a device 1300 that is pixilated byselective activation of portions of a stack of light-emitting layers.The device 1330 includes various light-emitting layers, each of whichhave a corresponding transparent cathode, and each of which share acommon transparent anode. The common anode is divided into separatesegments, and activation of a particular segment of the anode and one ofthe cathodes causes light from the corresponding portion of thelight-emitting layers to be emitted.

In greater detail, the device 1300 includes a blue-light emitting layer1310, a green-light emitting layer 1320, and a red-light emitting layer1330. A transparent cathode 1340 contacts the blue-light emitting layer1310, a transparent cathode 1350 is positioned between the blue-lightemitting layer 1310 and the green-light emitting layer 1320, and atransparent cathode 1360 is positioned between the green-light emittinglayer 1320 and the red-light emitting layer 1330. A transparent anode1370 is segmented into portions 1371-1375 such that light is emittedfrom a particular light-emitting layer, and from a particular portion ofthe light-emitting layer, depending on which portion of the anode 1370is activated. For example, activating the anode portion 1372 and thecathode 1360 causes red light 1380 to be emitted from the red-lightemitting layer 1330.

The device 1300 also includes optically active reflective layers 1385,1390, and 1395 deposited on a transparent substrate 1380. The opticallyactive reflective layers 1385, 1390, and 1395 are tuned to reflect,respectively, blue light, green light, and red light. Continuing withthe example of the red light 1380, the red light 1380 reflects off ofthe optically active reflection layer 1395, propagates up through theother optically active layers 1385 and 1390, neither of which reflectred light, through the transparent anode 1370, the light emitting layers1310, 1320, and 1330, and the cathodes 1340, 1350, and 1360 to exit thedevice 1300 through the transparent cathode 1370.

Thus, FIGS. 8A-8C, 9A-11A, 9B-11B, 12, and 13 all show a transparentdevice that includes an optically active reflective layer that causesthe device to preferentially emit light from one side of the device. Thespectral content of the emitted light is controllable through the tuningof the reflection band of the optically active layer or layers. A usermay see through such a device, thus, in addition to displays, inimplementations where pixilated optically active reflectors are used orwhere optically active layers with a single chirality (i.e. left- orright-handed) are used, these devices may be placed in the line-of-sightof a user and used to illuminate a region in view of the user.

In addition to being used in the standard displays mentioned above, thetransparent light emitting device may be used in transparent head-updisplays (HUDs) for the display of information or for use in virtual oraugmented reality applications. A head-up display may be a transparentdisplay that presents visual data in the line-of-sight of a user suchthat the user may view the data without having to look away from theirusual viewpoint. The TOUPLED discussed above may be used in a variety ofhead-up displays. For example, the TOUPLED may be used in vehicular HUDand general illumination applications such as applications that displayinformation on a vehicle's windshield (e.g., aircraft, automobile,motorcycle), automobile signal lights, air traffic control, and visuallanding aid lighting.

The TOUPLED also may be used in helmet-mounted HUD applications such asaircraft pilot visor HUDs, combat solider embedded helmet HUDs, embeddedprotective helmet visor HUDs used by, for example, search and rescueworkers, and visors used by athletes, such as football helmet visors.Additionally, the TOUPLED may be used in architectural HUD applications,such as digital signage (e.g. billboards, “spectacular” or architecturaldisplays on buildings), retail displays used for narrowcasting, andwindow-mounted or embedded displays. The TOUPLED also may be used inpersonal electronic device applications, such as near-eye head-updisplays, in which the TOUPLED display device is integrated on to a headmounted apparatus such as a pair of eyeglasses, sunglasses or visor.Such devices may be utilized for virtual reality or augmented realityapplications. In some implementations, the TOUPLED may be part of a verynear-eye display, in which the TOUPLED display device is integrated on acurved surface intended for direct contact with the eye such as acontact lens. The TOUPLED device also may be used with personal desktopand laptop computer displays, portable electronics devices such as PDAs,cellular phones, digital music players, digital game players, GPSdevices, and electronic readers.

The TOUPLED also may be used in photo-sensitive devices in which theTOUPLED transparent display pixel matrix is interlaced withphoto-detectors on an integrated circuit, such as a Complimentary-MetalOxide Semiconductor (CMOS) circuit. The TOUPLED also may be used instereoscopic displays for three-dimensional viewing of electronicimages. In a stereoscopic display, two images are created from a singleTOUPLED display device. Each of the images is generated withspin-polarized TOUPLED pixels that emit pure, or nearly pure, helicallypolarized light. Such a system may require the viewer to wear eye-wearpossessing polarized filtered lenses to permit each eye to perceive thetwo separate images generated by the display.

TOUPLEDs also may be used in dual-sided transparent displayapplications. In such displays, two TOUPLED devices are joined so thatthe respective optically active blocking layers of each device areadjacent to each other. Light is emitted from each device in opposingdirections to create a display that is active on two sides that areopposite to each other. The TOUPLED also may be used for illuminating anarea and in active electro-optical camouflage systems.

TOUPLED devices may be used for in-line-of-sight illumination for tasklighting. For example, TOUPLEDs may be used in a head-mounted apparatusto provide head-mounted illumination. Because the TOUPLED is transparentand emits light from one side, the head-mounted apparatus may be mountedin the line of sight of the user such that the region in theline-of-sight of the user is illuminated while the user also views theregion through the TOUPLED. TOUPLEDs also may be used in systems thatuse and/or provide visual feedback. For example, TOUPLED devices may beintegrated on an industrial or medical boroscope lens, a microscopelens, and other inspection devices. TOUPLED devices also may be usedwith or integrated with cameras.

It is understood that other modifications are within the scope of theclaims. For example, although red, blue, and green light-emitters arediscussed above, other colors may be used.

1. A method of fabricating a polarized light-emitting device, the methodcomprising: forming a radiation-emitting layer, the radiation-emittinglayer comprising a radiation-emitting material configured to emitradiation having a wavelength included in an emission wavelength bandand being disposed between a transparent anode and a transparentcathode; depositing an optically active reflective layer on thepolarized light-emitting device, the optically active reflective layerbeing configured to reflect radiation having a wavelength included in areflection wavelength band of the optically active reflective layer; andadjusting the reflection wavelength band of the optically activereflective layer to at least partially encompass the emission wavelengthband of the radiation-emitting layer.
 2. The method of claim 1, whereinthe radiation-emitting material comprises an organic light-emittinglayer.
 3. The method of claim 1, wherein the optically active reflectivelayer comprises a layer of glass-forming chiral nematic liquid crystals(GLC).
 4. The method of claim 3, wherein adjusting the reflectionwavelength band of the optically active reflective layer comprises:heating the layer of glass-forming chiral nematic liquid crystals abovea glass transition temperature (Tg) and near a critical point (Tc) ofthe glass-forming chiral nematic liquid crystals; irradiating theoptically active reflective layer with electromagnetic radiation for atime duration sufficient to alter the reflection wavelength band of theoptically active reflective layer to at least partially encompass theemission wavelength band of the radiation-emitting material; and coolingthe optically active reflective layer to a temperature below the glasstransition temperature (Tg).
 5. The method of claim 4, whereinirradiating the optically active reflective layer comprises irradiatingthe optically active reflective layer with ultraviolet (UV) radiation.6. The method of claim 3, wherein adjusting the reflection wavelengthband of the optically active reflective layer comprises adjusting amolecular composition of the layer of glass-forming chiral nematicliquid crystals.
 7. The method of claim 3, wherein: the optically activereflective layer comprises a first GLC film made of a right-handedglassy cholesteric material, and a second GLC film made of a left-handedglassy cholesteric material, the second GLC film being adjacent to thefirst GLC film, and adjusting the reflection wavelength band of theoptically active reflective layer comprises adjusting a molecular ratioof the right-handed glassy cholesteric material to the left-handedglassy cholesteric material.
 8. The method of claim 7, wherein, toadjust the reflection band of the optically active reflective layer, themolecular composition of both the first GLC film and the second GLC filmare adjusted.
 9. The method of claim 1, wherein adjusting the reflectionwavelength band of the optically active reflective layer results inchanging a width of the reflection wavelength band.
 10. The method ofclaim 1, wherein the radiation-emitting material comprises an inorganiclight-emitting layer.
 11. The method of claim 10, wherein the inorganiclight-emitting layer is a quantum dot layer.
 12. The method of claim 1,further comprising: depositing a second optically active reflectivelayer on the optically active reflective layer, the second opticallyactive reflective layer and the optically active reflective layer havingopposite chirality; and adjusting the reflection wavelength band of thesecond optically active reflective layer to at least partially encompassthe emission wavelength band of the light-emitting layer.
 13. The methodof claim 12, wherein the optically active reflective layers aredeposited consecutively, the reflection wavelength band of the secondoptically active reflective layer is adjusted on a separate substrate,and the optically active reflective layer is bonded to one side of thepolarized light emitting device after the reflection wavelength band ofthe second optically active reflective layer is adjusted.
 14. The methodof claim 1, wherein the optically active layer is deposited on atransparent substrate.
 15. The method of claim 14, wherein thetransparent substrate is located between the optically active reflectivelayer and the light-emitting layer.
 16. The method of claim 1, whereinthe optically active reflective layer comprises a holographic opticalrecording material layer; and wherein adjusting the reflectionwavelength band of the optically active reflective layer comprises:irradiating a holographic optical recording material layer with two ormore collimated object beams that successively interfere with a commoncollimated reference beam to generate several multiplexed reflectionholograms on the holographic optical recording material layer, whereinthe object beams are circularly polarized, have the same chirality, havea specified wavelength to at least partially encompass the emissionwavelength band of the radiation-emitting layer, and are incident to theholographic optical recording material layer at a series of angleschosen to maximize the reflection efficiency over a desired field ofview at the specified wavelength.
 17. The method of claim 1, whereinadjusting the reflection wavelength band of the optically activereflective layer results in changing the incident angles at which thereflection wavelength band is achieved.
 18. The method of claim 1,wherein the optically active reflective layer has a chirality, such thatthe optically active reflective layer is configured to reflect radiationhaving a chirality matching the chirality of the optically activereflective layer; and and wherein the method further comprises adheringa pre-fabricated broad-band circular polarization filter between thelight-emitting layer and the optically active reflective layer, whereinthe circular polarization filter has a chirality that is opposite thechirality of the optically active reflective filter.
 19. The method ofclaim 1, further comprising: adhering a prefabricatedradiation-collimating layer between the radiation-emitting layer and theoptically active reflective layer, wherein the radiation-collimatinglayer has an optical property of limiting the direction of radiationthat is emitted by the radiation-emitting layer to an angle less than 40degrees from normal relative to a surface of the polarized lightemitting device.
 20. The method of claim 19 wherein the prefabricatedradiation-collimating layer is one of a photonic crystal composite filmor a micro-louver film.